CH2(COO)2Cu·2H2O热分解的非等温动力学研究

The thermal dehydration and decomposition kinetics of CH₂(COO)₂Cu·2H₂O were investigated using the non-isothermal method by thermogravimetry (TG) technique in N₂. The iterative iso-conversional methods were applied to calculate the activation energy E_a of dehydration and decomposition， and the most probable mechanism function G(α) was determined by means of the master plots method. The pre-exponential factor A was obtained on the basis of E_a and G(α). Kinetic parameters (E_a and lnA) of dehydration were given as: E_a=139.79 kJ·mol^-1， ln(A/s^-1)=47.38. The mechanism function of the dehydration was G(α)=[-ln(1-α)]^2/3， and the decomposition of CH₂(COO)₂Cu proceeds to completion by two distinct reactions. These two reactions overlap in the transition process (0.45<α<0.65). Kinetic parameters (E_a and lnA )of the first reaction of decomposition were: E_a=201.15 kJ·mol^-1， ln(A/s^-1)=52.29， and the mechanism function was G(α)=[1-α]^-0.37. And in the second reaction G(α)=α+(1-α)ln(1-α)， E_a=156.74 kJ·mol^-1， ln(A/s^-1)=39.58.     

NO2对Cu/SAPO-34分子筛催化剂上NH3选择性催化还原NO性能的影响

主要考察了NO₂对Cu/SAPO-34 分子筛催化剂在整个温度范围内（100-500 ℃）NH₃选择性催化还原（SCR）NO性能的影响. 研究所使用样品为新鲜Cu/SAPO-34 催化剂在750 ℃下水热处理4 h 的稳定期样品.通过X射线衍射（XRD）和扫描电子显微镜（SEM）对样品的结构以及形貌进行表征,采用SCR活性评价、动力学实验以及原位漫反射傅里叶变换红外光谱（in situ-DRIFTS）表征催化剂的性能以及催化剂表面物种的变化. 活性评价实验结果表明,NO₂会抑制催化剂的低温（100-280 ℃）活性,但其存在会提高催化剂的高温（280 ℃以上）活性. 与此同时,随着反应物中NO/NO₂的摩尔比例减少,由于NH₄NO₃物种的分解,副产物（N₂2O）的浓度增大. 动力学结果表明,Cu/SAPO-34 催化剂上快速SCR反应的表观活化能（E_a=64.02 kJ·mol^-1）比标准SCR反应的表观活化能（E_a=48.00 kJ·mol^-1）更大. In situ-DRIFTS实验结果表明NO比NO₂更容易在催化剂表面形成硝酸盐,并且NO₂更容易与吸附在Brønsted 酸性位上的NH₃物种反应生成NH₄NO₃. 低温下,催化剂表面的NH₄NO₃物种会覆盖SCR反应的活性位,造成活性降低,但在高温时,形成的NH₄NO₃物种一部分会被NO还原为N2,而另一部分会直接热分解为N₂O,造成催化剂的选择性降低.     

NO2气相硝化金刚烷的计算研究

运用密度泛函理论(DFT)和半经验MO-PM3方法研究了NO₂气相硝化金刚烷反应机理. 计算结果表明, NO₂不能直接取代金刚烷H; 在B3LYP/6-311＋＋G(3df,2pd)//B3LYP/6-31G* 较高水平下, 对三个可能机理的反应势垒(E_a)的精确计算表明, 该反应的决速步骤为NO₂中O和N进攻1-H的竞争过程, 且1-硝基金刚烷为主要产物. NO₂中O进攻1-H决速反应过程中, 分子几何、原子自然电荷及IR光谱变化表明, C—H键的断裂和N—H键的形成是一个协同过程; 参与新键形成和旧键断裂原子C(1), H(11), O(28), O(29)和N(27)的原子自然电荷及与其相关的键长、键角有明显的变化. 反应过程中体系偶极矩的变化表明, 极性溶剂能降低反应势垒, 有利于反应的进行.     

La3ScBi5的合成与晶体结构

在氩气保护下，将金属单质置于钽管中进行高温固相反应得到了一个新的三元极性金属间化合物,La₃ScBi₅。通过X-射线单晶衍射确定了它的晶体结构。La₃ScBi₅晶体属六方晶系，空间群为P6₃/mcm(No.193)，晶胞参数为：a=b=0.975 73(5) nm，c=0.655 92(6) nm，V=0.543 41(9) nm³，Z=2。La₃ScBi₅属反式Hf₅Sn₃Cu结构类型，其结构特征为Bi的一维直线链和由ScBi₆八面体之间通过共面形成的{ScBi₃}链。能带计算表明La₃ScBi₅呈金属导电性。     

PSF/TiO2杂化超滤膜形成过程的热力学和动力学研究

采用溶胶-凝胶法制备了不同纳米TiO₂含量的聚砜(PSF)/TiO₂杂化超滤膜, 研究了TiO₂浓度对聚砜铸膜液流变学及热力学性质的影响, 构建了计算成膜过程中表观扩散系数(D_a)的新方法, 求出不同TiO₂浓度及温度下的D_a值, 进而剖析了铸膜液流变学和热力学性质的变化对成膜动力学的影响. 并通过扫描电镜观察、杂化膜孔隙率和超滤性能的测试考察了表观扩散系数与膜结构和性能的关系. 结果表明, 加入TiO₂溶胶的PSF铸膜液由牛顿流体转变为非牛顿流体, 其粘度随TiO₂浓度增大而增大. TiO₂的加入减小了铸膜液对非溶剂的容纳能力, 加速铸膜液的液-液相分离, 同时TiO₂引起的热力学促进作用和流变学阻碍作用相互竞争, 共同影响D_a的变化. 实验得出, D_a随温度升高而增大, 随TiO₂浓度的增大有先增大后减小的趋势. 表观扩散系数D_a与膜的结构和性能具有很好的相关性并能直观地描述整个成膜过程.     

NO2气相硝化金刚烷的计算研究

运用密度泛函理论(DFT)和半经验MO-PM3方法研究了NO₂气相硝化金刚烷反应机理. 计算结果表明, NO₂不能直接取代金刚烷H; 在B3LYP/6-311＋＋G(3df,2pd)//B3LYP/6-31G* 较高水平下, 对三个可能机理的反应势垒(E_a)的精确计算表明, 该反应的决速步骤为NO₂中O和N进攻1-H的竞争过程, 且1-硝基金刚烷为主要产物. NO₂中O进攻1-H决速反应过程中, 分子几何、原子自然电荷及IR光谱变化表明, C—H键的断裂和N—H键的形成是一个协同过程; 参与新键形成和旧键断裂原子C(1), H(11), O(28), O(29)和N(27)的原子自然电荷及与其相关的键长、键角有明显的变化. 反应过程中体系偶极矩的变化表明, 极性溶剂能降低反应势垒, 有利于反应的进行.     

三元配合物Tm[(C5/sub>H8NS2)3(C12H8N2)]的热化学性质研究

在无水乙醇中，用吡咯烷二硫代氨基甲酸铵(APDTC)和1,10-邻菲咯啉(o-phen·H₂O)与TmCl₃·3.65H₂O作用，合成了未见文献报道的三元固态配合物，确定它的组成为Tm[(C_{5/sub>H8NS2)3(C12H8N2)]。 用RD496-Ⅲ微量热计测定了298.15 K下水合氯化铥及两个配体在无水乙醇中的溶解焓，两个配体醇溶液的混合焓及不同温度下标题化合物液相生成反应的焓变。在实验和计算基础上，得到了液相生成反应的热力学参数(活化焓、活化熵和活化自由能)，速率常数和动力学参数(表现活化能、频率因子和反应级数)。通过合理的热化学循环，求得了298.15 K时标题化合物的固相生成反应焓变；推导了用该热量计测定固态物质比热容的计算式，并测定了题目配合物298.15 K的比热容。用RBC-Ⅱ精密转动弹热量计测定了题目配合物的恒容燃烧热， 计算了它们的标准摩尔燃烧焓和标准摩尔生成焓。}     

超分子化合物 [Eu(C10H9N2O4)(C10H8N2O4)(H2O)3]2·phen·4H2O 的热分解非等温动力学

用非等温热重法研究了Eu(III)的化合物[Eu(C₁₀H₉N₂O₄)(C₁₀H₈N₂O₄)(H2O)₃]₂·phen·4H₂O 的热分解及其动力学，并用Kissinger和Ozawa 方法计算了第一分解阶段的活化能.     

稀土高氯酸盐-谷氨酸配合物[Pr2(L-α-Glu)2(ClO4)(H2O)7](ClO4)3•4H2O的低温热容和热化学研究

合成了一种稀土高氯酸盐-谷氨酸配合物. 经TG/DTG、化学和元素分析、FTIR及与相关文献对比, 确定其组成为[Pr₂(L-α-Glu)₂(ClO₄)(H₂O)₇](ClO₄)₃•4H₂O, 纯度为99.0%以上. 利用显微熔点仪分析发现其没有熔点. 在78～370 K温区, 用精密绝热量热仪测量其低温热容, 在285～306 K温区发现一明显吸热峰, 归结为固-固相变过程. 通过相变温区三次重复热容测量, 得到相变温度T_tr、相变焓Δ_trH_m和相变熵Δ_trS_m分别为(297.158±0.280) K, (12.338±0.016) kJ•mol^－1和(41.520±0.156) J•K^－1•mol^－1. 用最小二乘法将非相变温区的热容对温度进行拟合, 得到了热容随温度变化的两个多项式方程. 用此方程进行数值积分, 得到每隔5 K的舒平热容值和相对于273.15 K的热力学函数值. 根据TG/DTG结果, 推测了该配合物的热分解机理. 依据Hess定律, 选择1 mol•dm^－3盐酸为量热溶剂, 利用等温环境溶解-反应量热计, 测定了该配合物的标准摩尔生成焓为: Δ_fH_m⁰＝－(7223.1±2.4) kJ•mol^－1.     

3-硝基-1，2，4-三唑-5-酮铅金属盐快速热分解反应动力学研究

利用温度快速跃升傅立叶变换红外原位分析技术对3-硝基-1，2，4-三唑-5-酮铅盐的快速热分解反应动力学进行了研究。借助快速升温过程中Pt金属丝的控制电压变化曲线得到剧烈放热峰的诱导出现时间t_x，利用t_x值计算得到了快速热分解过程的动力学参数。在0.1 MPa氩气气氛，230～270 ℃实验温度范围内，3-硝基-1,2,4-三唑-5-酮铅金属盐的活化能E_a=94.0 kJ·mol^-1，lnA=20.5。同时得到了该化合物快速热分解过程的近似吉布斯自由能变，熵变和焓变。该方法借助温度快速跃升技术，在模拟材料实际使用情况下计算得到其动力学参数，可用于含能材料燃烧模型的建立。     

DSC and X-ray Diffraction Study of Polymorphism in n-Alkylammonium Chlorides

The influence of the hydrocarbon chain length in the formation of interdigitated and non-interdigitated bilayers in n -alkylammonium chlorides has been investigated for chain lengths varying between 8 and 14 carbon atoms. The formation of non-interdigitated bilayers during crystallization from solution is favoured for shorter chains whilst the interdigitated structure is predominant for larger chains. The thermodynamic parameters of the solid to solid phase transitions in the non-interdigitated samples depend on chain length showing the odd-even alternation that characterized homologous series in n -paraffins. The solid to liquid crystal phase transition temperatures and enthalpies show a linear dependence with the chain length. This revised version was published online in July 2006 with corrections to the Cover Date.     

The influence of the size and position of the alkyl groups in alkylimidazole molecules on their acid‐base properties

Dissociation constants of HL⁺ acids, where L stands for 1‐alkylimidazole, 1‐alkyl‐2‐methylimidazole, 1‐alkyl‐2‐ethylimidazole, 1‐alkyl‐2‐propylimidazole, 1‐alkyl‐4‐methylimidazole and 1‐alkyl‐2‐ethyl‐4‐methylimidazole, were determined potentiometrically. For each of the homologous series of these bases, a relationship has been derived between the pK_a value and the number of carbon atoms in the hydrocarbon group for (CH₂)_n ≤ 13. The basicity of the alkylimidazoles has been found to increase linearly with increasing carbon chain length. The slopes of straight plots of pK_a = f(n_CH2) have been found to increase with increasing basicity of homologous series of the alkylimidazoles.     

Bromine-terminated azobenzene liquid crystals

A series of liquid crystals (LCs) of bromine-terminated azobenzene were synthesised and characterised. The LCs were composed of an azobenzene core, an alkyl chain and a flexible spacer with a bromine atom at a remote position. Mesomorphic properties were dependent on both the alkyl chain length and the relative position of the bromine atom at the end of the spacer group. The nematic phase was favoured over the smectic A phase for alkyl chains with one and seven carbon atoms. However, the SmA mesophase was dominant for compounds with 10-carbon alkyl chains. The remote bromine atom in the spacer group favoured SmA for homologous with n-decyl chains and the nematic phase for n-heptyl and methyl groups. Molecular modelling showed that the azobenzene LCs tended to adopt the all trans-conformation in the gas phase as the number of carbon atoms increased. For short spacer groups, bent conformations contributed to the level population proportion of conformers. For the non-LC 5a, the gauche conformation became the most stable with a torsional angle of –68.9°. X-ray experiments showed a monolamellar SmA mesophase in an antiparallel arrangement. Absorption maxima at 360 and 440 nm were assigned to π–π* and n–π* transitions, respectively.     

Self-diffusion in the isotropic phase of the p-alkoxybenzoic acid homologous series

The temperature dependence of the self-diffusion coefficients of those members of the p-alkoxybenzoic acid homologous series with n = 3 to 8 alkyl chain carbon atoms has been measured in the isotropic liquid phase and a comparison has been made between the activation energies for self-diffusion in the liquid and the solid phase. The self-diffusion coefficients at the isotropic-nematic transition temperatures were found to decrease monotonically with increasing number of alkyl chain carbon atoms.     

Excess Molar Volumes and Excess Partial Molar Volumes of Triethylene Glycol Monomethyl Ether–n-Alcohol Mixtures at 25°C

The excess molar volumes V ^E have been measured for binary mixtures of triethylene glycol monomethyl ether with methanol, ethanol, 1-propanol, 1-pentanol, and 1-hexanol as a function of composition using a continuous–dilution dilatometer at 25°C at atmosphere pressure. V ^E are negative over the entire range of composition for the systems triethylene glycol monomethyl ether + methanol, + ethanol, and + 1-propanol, and positive for the remaining systems, containing 1-pentanol and + 1-hexanol. V ^E increases in a positive direction with increasing carbon chain length of the n-alcohol. The excess partial molar volumes V _i ^E of the components were evaluated from the V ^E results. The behavior of V ^E and V _i ^E with composition and the number of carbon atoms in the alcohol molecule is discussed.     

The thermal behaviour of mixed long chain alkylammonium tetrachloromanganates(II)

The results of a calorimetric and structural investigation of mixtures of layer compounds of the kind (RNH₃)₂MCl₄, R being a long chain n-alkyl group, show that the low-temperature forms are solid solutions, mainly ordered from the conformational viewpoint, in which chains of different length are more or less randomly arranged on the surface of the anionic layers. The observed high enthalpy solid—solid phase transitions correspond to the “melting” of the hydrocarbon layers, giving solid solutions in which the conformational freedom of the alkyl chains is similar to that of hydrocarbon substances in the liquid state.     

Synthesis and characterization of poly-n-alkylmalonamides: Formation of a partially disordered layer structure

Polyamides from n-alkylmalonic acids and linear aliphatic diamines, with paraffinic side chains of 3–18 carbon atoms, were prepared by melt polycondensation or by low-temperature interfacial polycondensation and were characterized by infrared, differential scanning calorimetry (DSC), and x-ray diffraction techniques. First-order transitions were found in the range of 130–210°C, depending on the number of carbon atoms in the side chain. The x-ray diffraction indicated substantially amorphous systems for polyamides with 8–18 carbon atoms in the side chain. However, long-range order arises in these polymers from a solid-state structure in which polyamide and hydrocarbon layers having partially disordered chain conformations alternate.     

Phase separation in the (R4N)2[Nd(NO3)5]-hydrocarbon solvent-chloroform systems at various temperatures

Phase diagrams were studied for (R₄N)₂[Nd(NO₃)₅]-C _n H_{2n + 2}-chloroform liquid ternaries (where R₄N⁺ is trialkylbenzylammonium and n = 10, 12, 14, or 15) at T = 298.15−333.15 K. (R₄N)₂[Nd(NO₃)₅]-C _{n H2n + 2} binaries are two-phase liquid systems at all temperatures in this range. One phase (phase I) is an almost pure hydrocarbon solvent. The other (phase II) is enriched in (R₄N)₂[Nd(NO₃)₅]. The C _n H_{2n + 2} solubility in phase II decreases with increasing the alkyl chain length of the hydrocarbon solvent and increases with increasing temperature. The title liquid ternaries are characterized by a homogeneous solution field and a two-phase liquid solution field. One phase is enriched in (R₄N)₂[Nd(NO₃)₅] and chloroform; the other is enriched in the hydrocarbon solvent. Liquid-liquid phase separation fields enlarge with increasing C _n H_{2n + 2} alkyl chain length and slightly narrow with increasing temperature. Critical solution points at fixed temperatures depend on C _n H_{2n + 2}. Original Russian Text ? A.K. Pyartman, V.A. Keskinov, P.V. Zaitsev, 2009, published in Zhurnal Neorganicheskoi Khimii, 2009, Vol. 54, No. 3, pp. 531–534.     

π-Selective stationary phases: (I) Influence of the spacer chain length of phenyl type phases on the aromatic and methylene selectivity of aromatic compounds in reversed phase high performance liquid chromatography

Phenyl type stationary phases of increasing spacer chain length (phenyl, methyl phenyl, ethyl phenyl, propyl phenyl and butyl phenyl, with 0–4 carbon atoms in the spacer chain, respectively) were synthesised and packed in house to determine the impact that the spacer chain length has on the retention process. Two trends in the aromatic selectivity, q_aromatic, were observed, depending on whether the number of carbon atoms in the spacer chain is even or odd. Linear log k′ vs ? plots were obtained for each stationary phase and the S coefficient was determined from the gradient of these plots. For the phenyl type phases, the S vs n_c plots of the retention factors of linear polycyclic aromatic hydrocarbons vs the number of rings exhibit a distinct discontinuity that between 3 and 4 rings, which increases with increasing spacer chain length for even phases but decreases for odd phases. Accordingly, we suggest that the retention factors depend differently on the number of carbon atoms in the spacer chain depending on whether this number is even or odd and that this effect is caused by different orientations of the aromatic ring relative to the silica surface.     

Aqueous Phase Behavior of Diglycerol Fatty Acid Esters

We have studied the phase behavior of homologous series of diglycerol fatty acid esters (Qn‐D, for n=10, 12, 14, and 16, where n represents the carbon number in the alkyl chain length of amphiphile) in aqueous solution as a function of temperature and surfactant concentration. The different equilibrium phases present over a wide range of composition and temperature studied were characterized by means of visual observation under normal and polarized light, and x‐ray scattering techniques at small (SAXS) and wide angle (WAXS) regions. In diglycerol monocaprate (Q10‐D) and diglycerol monolaurate (Q12‐D)/H₂O systems, lamellar liquid crystal (L_α) phase is present in the surfactant rich region and it swallows an appreciable amount of water. The amount of water swallowed by the L_α phase was determined by plotting the interlayer spacing, d, as a function of reciprocal of the surfactant weight fraction W_s . In the dilute regions, dispersion of L_α phase in water is observed over a wide range of temperature. At higher temperatures, the L_α phase melts to isotropic two‐liquid phases in water rich region whereas to isotropic reverse micellar solution (O_m) in surfactant rich region. The L_α‐O_m transition temperature is increased on increasing the hydrocarbon chain length of the surfactant from Q10‐D to Q12‐D. There is surfactant solid phase in equilibrium with water up to 25°C in diglycerol monomyristate (Q14‐D)/H₂O system and the solid phase could solubilize 25 wt% water. The melting temperature of solid phase is practically constant in a wide range of compositions. Both the solid present region and the extent of water solubilization are increased in diglycerol monopalmitate (Q16‐D)/H₂O system. At lower surfactant concentrations, excess water appears and dispersion of solid in water is formed. The structure of the solid is identified by WAXS measurement and it is confirmed to α‐solid. Normal vesicular aggregates are formed in L_α+W regions in the Q14‐D/H₂O system at 25°C.